This invention relates in general to diesel engines for vehicles and in particular to a device for testing a solid state glow plug controller for a diesel engine while the controller remains mounted upon the engine.
Diesel engines do not use spark plugs. Rather, they rely upon compression of an air-fuel mixture by rapid motion of a piston to ignite the fuel in a combustion chamber. However, it is known to use glow plugs to aid combustion during engine start-up. Such glow plugs are typically operated for only a brief time period.
The glow plugs mounted upon a diesel engine are typically controlled by a glow plug controller, which is mounted directly upon the engine block. Upon the vehicle operator turning on the vehicle ignition, the glow plug controller applies a high DC current, often in the neighborhood of 150 amps, to the glow pugs to rapidly heat the combustion chamber. The initial application of current is usually referred to as a xe2x80x9cpre-glowxe2x80x9d mode of operation. A temperature sensor included in the controller detects the engine temperature and controls the duration of the pre-glow, which typically lasts from three to eight seconds.
Following the pre-glow portion of the engine starting cycle, the controller transitions to an xe2x80x9cafter-glowxe2x80x9d mode of operation. During the after-glow portion of the engine starting cycle, the controller generates a pulsed voltage which is applied to the glow plugs. The duration of after-glow is a function of the sensed engine temperature. It is known for a controller to reduce the duty cycle of pulsed voltage as the engine temperature approaches glow plug cut-off.
Because of thee currents drawn by the glow plugs, the output voltage generated by the controller is typically applied to the coil of an electro-mechanical relay. The electro-mechanical relay is connected between the power supply and the glow plugs and regulates the actual glow plug current. Typically, the electro-mechanical relay is located remotely from the glow plug controller to protect the unit from the engine heat; however, the relay can be included in the controller.
This invention relates to a device for testing a solid state glow plug controller while the controller remains mounted upon a diesel engine.
When a diesel engine fails to start, the problem is often due to failed glow plugs or a failed glow plug controller. In order to test a glow plug controller, it is necessary to remove the unit from the vehicle engine. Accordingly, it would be desirable to provide a device for testing a glow plug controller while the controller remains mounted upon the engine.
The present invention contemplates a test device which includes a connector adapted to be electrically connected to the glow plug electrical connector. The test device also includes a first lead extending from the connector which is adapted to be connected to a vehicle power supply, and a second lead also extending from the connector which is adapted to be connected to a vehicle ground. A visual display is mounted upon the connector and electrically connected to the second lead. When the test device is connected the glow plug controller, the visual display is electrically connected through the glow plug controller to the power supply and is operative to indicate the condition of the glow plug controller.
In the preferred embodiment, the visual display included a light emitting diode connected in series with a load resistor. Flashing of the light emitting diode is an indication that the glow plug controller is functional.
Also in the preferred embodiment, the test device electrical connector is a female connector having a plurality of sockets and the first lead is connected to a first socket and a second socket in the connector. The light emitting diode has an anode and a cathode with the anode connected to a third socket in the female connector. Additionally, the load resistor has a first end and a second end with the first end connected to the diode cathode and the second end connected to the second lead, the second lead being connected to a fourth socket in the female connector.
The invention further contemplates an adapter for using the test device with a glow plug controller having a female electrical connector. The adapter includes a male connector having a plurality of pins which are received by the sockets in the test device female electrical connector and a plurality of leads which are adapted to be connected to the female electrical connector for the glow plug controller. The adapter includes an adapter load resistor which is adapted to be connected between the voltage output socket of the glow plug controller and ground. The adapter also can include an optional thermistor which, when included, is connected between the adapter load resistor and ground.
The invention also contemplates a procedure for testing a glow plug controller which is mounted upon a vehicle engine. The procedure includes the steps of disconnecting the vehicle wiring harness from the electrical connector for the glow plug controller being tested and connecting the electrical connector of the test device described above to the glow plug controller electrical connector. One of the test device leads is connected to the vehicle power supply and the other of the test device leads is connected to the vehicle ground. The visual indicator is then observed to determine that the glow plug controller is functioning properly. The above procedure is modified when the test device electrical connector is not compatible with the glow plug controller electrical connector by inserting the adapter described above between the test device and the glow plug controller electrical connector.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.